(1) Field of the Invention
The present invention relates to amorphous silica or silica-alumina spherical particles having a novel particulate shape and a process for the preparation thereof.
(2) Description of the Prior Art
Spherical particles of amorphous silica or silica-alumina are widely used as fillers for various films and other resins and rubbers, as fillers for cosmetics, as supporting carriers for perfumes and chemicals, as chromatography fillers and for other purposes.
Spherical amorphous silica has been prepared according to the process in which a silica hydrosol is sprayed or the spray is further caused to impinge to a fluid, the process in which an organic silicic acid compound is hydrolyzed, the process in which a glass ceramic is molded into a spherical shape and is sintered, and the like process.
However, silica or silica-alumina spherical particles prepared according to these processes have a relatively coarse primary particle size and a broad particle size distribution. Therefore, development of silica or silica-alumina spherical particles having a fine primary particle size and a sharp particle size distribution is eagerly desired in the art.
When such spherical particles are used as a filler for a resin, the dispersibility of the particles in the resin and the compatibility of the particles with the resin should be taken into consideration. For example, when a resin having spherical particles incorporated therein is formed into a film or the like and is then drawn, a problem of formation of voids between the resin and the filler particles often arises.